This means that there is a substantial amount of unnecessary air coming from your mask. This can usually be rectified by adjusting the mask fit. Refer to the troubleshooting section in your mask user guide.
If your mask fit is acceptable, your mask may be damaged and be in need of a replacement. The average life expectancy of a mask is 12 months. If you believe your mask is older than this, you may need to replace it as the quality may be compromised.